Computational models for predicting stresses in thin polycrystalline films, such as found in electronic interconnects and MEMS, are being developed. The stresses and stress gradients that arise due to thermal conditions and electromigration have a big influence on reliability. The model is based on a thermoelasto- viscoplastic crystal model modified to account for interactions between the film and substrate, the film and passivation layer, and neighboring grains. A model for grain boundary diffusion and lattice diffusion driven by electromigration and stress gradients is also being developed. These models are being implemented into an advance finite element framework. A procedure for meshing a general columnar grain structure with tetrahedral elements where element faces align with grain boundaries has been developed.
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